ARP entry on a specific interface of the SSR 130 keeps disappearing.

When I initiate a ping to the other end, the first packet times out, but then subsequent packets work fine.

However, when I stop the ping and start the ping, the first packet times out again.

The same cable functions normally when connected to a Juniper SRX.

The issue is because the Interface did not have active traffic (like in case if back up wan Link)

The arp entry is cleared after timeout as there is no active traffic and arp entry build only after the subsequent traffic

The issue will not be seen once there is active and is harmless.